The Use of Navigation During Total Knee Replacement Improves Precision in Achieving Mechanical Alignment in Obese Patients: A Short-Term Multicenter Randomized Clinical Trial.

Background: Obesity (body mass index ≥30 kg/m2) is a global health challenge and a known risk factor of knee osteoarthritis (KOA), increasing the need for total knee arthroplasty (TKA). Obese patients face higher risks of early implant failure and revision, often linked to malalignment. Navigation-assisted surgery (NAS) improves precision in achieving mechanical alignment, but its impact in obese patients remains underexplored. This randomized, controlled, open-label, multicenter trial evaluated short-term radiographic outcomes, focusing on coronal alignment, in obese patients undergoing TKA with NAS versus conventional instrumentation. The primary hypothesis was that NAS would result in a higher rate of mechanical axis alignment within a predefined target (180° ± 3°). Methods: A total of 159 obese patients with symptomatic KOA were randomized 1:1 at 2 hospitals to undergo TKA with either NAS or conventional guides. Mechanical axis alignment was assessed 1 year postoperatively using long-standing radiographs. Secondary end points included femoral and tibial component alignment, surgical time, complications, range of motion, Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, visual analog scale, and EuroQol-5D. Results: In total, 154 patients were analyzed. Proper mechanical axis alignment (180° ± 3°) was achieved in 69% of NAS cases vs. 47% in controls (p = 0.006; OR = 2.5; 95% confidence interval: 1.29-4.83). The mean deviation was -1.59° (SD 3.02) in NAS vs. -2.15° (SD 3.56) in controls. Tibial alignment outliers occurred in 16% (12/73) of NAS vs. 32% (23/71) in controls (p = 0.026). Surgical time was longer with NAS (70 min [interquartile range (IQR) 63-76] vs. 59 min [IQR 55-67], p < 0.001). No differences were found in complications or hospital stay. Functional outcomes improved similarly in both groups at 1 year. Conclusion: NAS significantly improves precision in achieving mechanical alignment in obese patients undergoing TKA. Despite similar clinical outcomes, NAS offers superior radiographic accuracy. Longer term studies are needed to assess effects on implant survival and patient-reported outcomes. Level of Evidence: Level I. See Instructions for Authors for a complete description of levels of evidence.